Twist-drill-point grinding and thinning machine



Nov. 8 192-7.

; H. W. HUNT ET AL TWIST DRILL POINT GRINDING AND THINNING MACHINE 3 Sheets-Sheet 1 Filed Feb. 10. 1927 Nov. 8, 192 7.

H. W. HUNT ET AL TWIST DRILL POINT GRINDING AND THINNING MACHINE 3 Sheets-Sheet 2 Filed Feb. 10, 1927 Nov. 8, 192 7.

H. W. HUNT ET AL TWIST DRILL POINT GRINDING AND THINNING MACHINE Filed Feb. I0. 1927 3 Sheets-Sheet 3 Patented Nov. 8, 1927.

um ser HERBERT WILLIAM HUNT AND PERCY HUNT, or on]: 'rnrirronn; MANCHESTER,

' v ENGLAND.

TWIsT-DRi L-r INT .eRi DINe AN r n Ne. acrame.

Application filed February 10, 1927, Serial No. 167,32 l, and in Great Britain @ecember Q1, 1926.

This invention refers to twist drill point rinding and thinning machines.

'i The object of the improvements is to provideimp'roved facilities for grinding out the flutesof the drill next the drill point and thusmaintaining the thickness (or thinness). of such point with each sharpening ofthe drill. f

In our prior Patent No. 1,448,7 i6, a small grinding wheel is provided for a like purpose, but the drill has to be fixed in one holder for grinding the cutting edges and in another and separate holder for grinding the flutes furthermore, the drill requires to be carefully set for each operation. According to this invention, a small grinding wheel is mounted so that the grind ing out of the flutes, or thinning the point, can be eliected whilst the drill is still in the holder for grinding the cutting edges, thus avoiding transference from one holder to another and also avoiding the need for resetting.

The invention will be described in detail with the aid of the accompanying drawings, wherein I Fig. l is a side elevation, and v Fig. 2 a plan view of so much of a twist drill grinding machine as is necessary to.

illustrate the invention;

Fig. 3 is a plan of the point of a drill and of the small grinding wheel used to grind the flutes.

Figs. 4 and 5 are side elevation and plan respectively to a larger scale, of a part of the machine shown in Fig. 1, and Figs. 6

and 7 are views of detail parts hereinafter de cribed.

In Figs. 1 and 2, a is a tray on which the main parts of the machine are mounted, the tray in turn being supported by a box casting or pedestal b. Journaled in bearing 0 is the shaft (Z to which is keyed the clamp for detachably securing the main grinding wheel 6 to said shaft, a. guard f enclosing themajor portion of the wheel. To the end of the shaft (Z is secured a disc 9 provided with a facing of leather or like yielding and frictional material 9 Rising from the tray a is a bracket it (see Fig. 6) from which extends a boss 2'. Rotatably mounted in the boss is a stem or shank part 3' of a T-shaped bearing member 7a. Mounted in said member is a hollow shaft 70 held to the hearing by closing the split end therein by a nut Z0 Journaled in" said shaft is a spindle l.

Keyed to said spindle" is a metal collar m tween the boss 2' and bearing is normally contacts withthe facing-g en the disc 9 andtransmits the motion of the disc to the ward end. of the spindle isaflute grinding which under the pressure of aspring bewheel -0, the'upper partsof thelwheel being covered by a'guard 19. In one with the bearingmember 72 is a lateral extension '(see' Fig. 7) through which passes a screw Z0 the point of which is adaptedto" contact with a; shoulder on the bracket h and limit the downward angular in ovenient of the wheel 0. A spring 9' may be provided to hold the wheel 0 raised when not in use.

Upon the front end of the boss are camv faces 1*, and to the end'ofthe shank j is fitted a pin y' which'be ars against the boss under the pressure of the spring 01.. Then the wheel 0 is raised the'shankj is rotated and its pin 7' caused to ride up. the cam.

faces 1 ,17 and thereby draw 'thecollar clear of the disc g, and stop rotation ofthe wheel 0. Contrawise, on the wheel being lowered,the pin moves down the'cam faces and allowsthe collar on to engagethe disc and start the wheel 0 rotating. T

The twist'drill to be ground and pointed is mounted in the usual holder carried upon a plate zf-pivotallymovable abouta stud [a supported upon a slide or carriage v. This latter is adapted to move to and'froon guides o and with the drill properly'positioned in the holder to move one of the cutting edges-0f the drill across the periphery:

of the grinding wheel 6 in the usual way.

After the cutting edges of the drill point have been sharpened, the carriage o is moved to a position opposite the. flute grinding wheel 0, when such wheel is brought down by hand to the angular position shownin Fig. 1, when its edge contacts with the sur-I face of the drill flute and grinds away a portion of the metal lying .next to the point and alongside oneof the cutting edges, see Fig. 3. The drill is then given a half turn in its holder, and the grinding wheel o'iis again. brought down and caused to grind away a portion of the metal lying neXt to the point and alongside the-other cutting edge of the drill, thereby thinning the point of the drill as Well as imparting a slight undercut to the cutting edges, h

To assist in quickly determlnmg the correct position of the drill after a half rotation, the collar 0c mayhave diametrically ope posite notches with which a lever y may engagewhen pressed down by hand, the lever being at other times held clear of the collar by a spring. 7

The movements of the side of the carriage.

I anism, 'or by the rack and pinion described I In the case of automatically controlled machines, the carriage will bemoved by hand after disengaging it fromits operating mechholder and a slidably mounted carriage on which the drill-holder support is pivoted,

' the combination therewith of a further but smaller grinidng wheel, means for rotatably supporting the smaller wheel alongside the main grinding wheel, means for transmitting the motion of the main grinding wheel shaft to the smaller grinding wheel, and means for positioning the smaller grinding wheel at an angle to the vertical and with its lower part at apoint' where on said carriage on which the drill-holder support .is mounted being moved in a' direction parallelwith the axis of the main grinding wheel, a portion of the drill next the drill point and neXt to one of the cutting edges is removed and the cross carriage 1) may be conveniently effected by a hand lever w piv- 'oted to the tray a and at the end of its shorter arm engaging a slot in the under section of the drill at set forth. a I

2. Intwist drill point grinding machines and in means for removing portions of the drill next the drill point and neXtto one of the cutting edges as claimed in claim 1, a T-shaped member with hollow head part and solid stem partyafixed bracket in which the solid stem part is slidably and rotatably journaled, ahollow and non-rotary shaft in said hollow head part of the T-shaped member, a spindle rotatably mounted in said ho l-V low shaft, a grmdm'gwvheel secured to one such parts thinned, as

end of said spindle, and a driving collarsecured to'its other end, a friction disc on the end of the main grinding wheel shaft, with the side face of which the periphery of. the

said collar may frictionally contact, a spring 7 for pressing the collar against the disc, and a cross pin and cam faces between the stem of the T-shaped member and the fiXedf bracket whereby on the Tshaped member being glven an angular movement in one direction, the'collar is caused to leave the disc and stop the rotations of the smaller grind ing wheel, while 'when given an angular movement in an opposite direction, the collar is allowed to engag'e'the disc and start the rotations of the smaller grinding wheel, regulatable means being provided between the fixed bracket and the T-shaped member for limiting the angular movements of the' latter in one direction and determining the position of the grinding wheel when required to operate upon the drill point, asset forth.

In testimony whereof we have signed our names to thisspecification.

HERBERT' M. HUNT.

PERoYnUNr. 

